MVC 3自定义DataAnnotation：将错误消息与特定属性相关联

Question

我已经在类上定义了一个类似于this one的自定义DataAnnotation属性，但确保至少填充了一个属性。它工作正常，并向模型ValidationSummary添加错误消息。但是，我希望能够将错误消息与特定属性（或任何字符串）相关联，以便我可以在我的视图中的特定位置显示它。

因此，如果我的自定义属性使用如下：

[RequireAtLeastOne(GroupId = 0, ErrorMessage = "You must specify at least one owner phone number.")]
public class UserViewModel: User {
    ...
}

然后我希望能说出类似的话：

[RequireAtLeastOne(GroupId = 0, ErrorMessage = "You must specify at least one owner phone number.", ValidationErrorKey = "my_key")]
public class UserViewModel: User {
    ...
}

...并在以下视图中使用它：

@Html.ValidationMessage("my_key")

如果我必须将错误消息与我的模型上的特定属性相关联而不是任意字符串，那也没关系。我怎么能做到这一点？

Answer 1

使用ryudice's answer和this question作为起点，我能够使用IValidatableObject解决此问题。对于任何感兴趣的人，这里是我最终的完整代码：

1。定义自定义验证属性RequireAtLeastOneAttribute

该属性在类上进行，以指示验证应检查属性组并确保填充每个组中的至少一个属性。此属性还定义了错误消息和ErrorMessageKey，它将用于跟踪错误消息并在视图中显示它们，而不是使用通用ValidationSummary集合。

[AttributeUsage(AttributeTargets.Class, AllowMultiple = true)]
public class RequireAtLeastOneAttribute: ValidationAttribute {

    /// <summary>
    /// This identifier is used to group properties together.
    /// Pick a number and assign it to each of the properties
    /// among which you wish to require one.
    /// </summary>
    public int GroupId { get; set; }

    /// <summary>
    /// This defines the message key any errors will be associated
    /// with, so that they can be accessed via the front end using
    /// @Html.ValidationMessage(errorMessageKey).
    /// </summary>
    public string ErrorMessageKey { get; set; }

    public override bool IsValid(object value) {
        // Find all properties on the class having a "PropertyGroupAttribute"
        // with GroupId matching the one on this attribute
        var typeInfo = value.GetType();
        var propInfo = typeInfo.GetProperties();
        foreach (var prop in propInfo) {
            foreach (PropertyGroupAttribute attr in prop.GetCustomAttributes(typeof(PropertyGroupAttribute), false)) {
                if (attr.GroupId == this.GroupId
                    && !string.IsNullOrWhiteSpace(prop.GetValue(value, null).GetString())) {
                    return true;
                }
            }
        }
        return false;
    }

}

2。定义自定义属性PropertyGroupAttribute

这将用于定义哪些属性组至少需要填充一个值。

[AttributeUsage(AttributeTargets.Property)]
public class PropertyGroupAttribute : Attribute {

    public PropertyGroupAttribute(int groupId) {
        this.GroupId = groupId;
    }

    public int GroupId { get; set; }

}

3。将属性附加到模型和属性

使用“GroupId”整数将属性组合在一起（可以是任何东西，只要它对于所有属性都是相同的，其中必须填写至少一个）。

[RequireAtLeastOne(GroupId = 0, ErrorMessage = "You must specify at least one owner phone number.", ErrorMessageKey = "OwnerPhone")]
[RequireAtLeastOne(GroupId = 1, ErrorMessage = "You must specify at least one authorized producer phone number.", ErrorMessageKey = "AgentPhone")]
public class User: IValidatableObject {

    #region Owner phone numbers
    // At least one is required

    [PropertyGroup(0)]
    public string OwnerBusinessPhone { get; set; }

    [PropertyGroup(0)]
    public string OwnerHomePhone { get; set; }

    [PropertyGroup(0)]
    public string OwnerMobilePhone { get; set; }

    #endregion

    #region Agent phone numbers
    // At least one is required

    [PropertyGroup(1)]
    public string AgentBusinessPhone { get; set; }

    [PropertyGroup(1)]
    public string AgentHomePhone { get; set; }

    [PropertyGroup(1)]
    public string AgentMobilePhone { get; set; }

    #endregion
}

4。在模型上实现IValidatableObject

public class User: IValidatableObject {

    ...

    #region IValidatableObject Members

    public IEnumerable<ValidationResult> Validate(ValidationContext validationContext) {
        var results = new List<ValidationResult>();

        // This keeps track of whether each "RequireAtLeastOne" group has been satisfied
        var groupStatus = new Dictionary<int, bool>();
        // This stores the error messages for each group as defined
        // by the RequireAtLeastOneAttributes on the model
        var errorMessages = new Dictionary<int, ValidationResult>();
        // Find all "RequireAtLeastOne" property validators 
        foreach (RequireAtLeastOneAttribute attr in Attribute.GetCustomAttributes(this.GetType(), typeof(RequireAtLeastOneAttribute), true)) {
            groupStatus.Add(attr.GroupId, false);
            errorMessages[attr.GroupId] = new ValidationResult(attr.ErrorMessage, new string[] { attr.ErrorMessageKey });
        }

        // For each property on this class, check to see whether
        // it's got a PropertyGroup attribute, and if so, see if
        // it's been populated, and if so, mark that group as "satisfied".
        var propInfo = this.GetType().GetProperties();
        bool status;
        foreach (var prop in propInfo) {
            foreach (PropertyGroupAttribute attr in prop.GetCustomAttributes(typeof(PropertyGroupAttribute), false)) {
                if (groupStatus.TryGetValue(attr.GroupId, out status) && !status
                    && !string.IsNullOrWhiteSpace(prop.GetValue(this, null).GetString())) {
                    groupStatus[attr.GroupId] = true;
                }
            }
        }

        // If any groups did not have at least one property 
        // populated, add their error messages to the
        // validation result.
        foreach (var kv in groupStatus) {
            if (!kv.Value) {
                results.Add(errorMessages[kv.Key]);
            }
        }

        return results;
    }

    #endregion
}

5。使用视图中的验证消息

验证消息将保存为您在ErrorMessageKey属性定义中指定的任何RequireAtLeastOne - 在此示例中为OwnerPhone和AgentPhone。

@Html.ValidationMessage("OwnerPhone")

注意事项

内置验证还会向ValidationSummary集合添加错误消息，但仅针对模型上定义的第一个属性。因此，在此示例中，只有OwnerPhone的消息会显示在ValidationSummary中，因为它是在模型上首先定义的。我没有找到解决方法，因为在我的情况下它并不重要。

Answer 2

您可以在模型上实现IValidatableObject并在那里执行自定义逻辑，它将允许您使用您想要的任何键添加消息。